<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Page break bug in vertical text</title>
    <style>
        @page {
            size: 140px;
            margin: 20px;
        }
        * {
            margin: 0;
        }
        html {
            writing-mode: vertical-rl;
            font-size: 20px;
            line-height: 20px;
        }
    </style>
</head>
<body>
ああああああああああああああここで改ページするはずああああああああああ
</body>
</html>